Which of the following is a system of standardized symbols used in the fire protection industry?

The answer C, NFPA 170, is correct because it specifically addresses the creation and use of a system of standardized symbols in the fire protection industry. NFPA 170 provides guidelines for the identification of fire and life safety-related symbols, which are essential for ensuring clarity and uniformity in safety-related signage, diagrams, and other visual aids. This standard helps professionals in the field to communicate effectively and reduce confusion when interpreting fire protection systems.

In contrast, the other NFPA options focus on different aspects of fire safety and electrical regulations. NFPA 300 does not exist; NFPA 70 pertains to the National Electrical Code which outlines electrical wiring and safety standards; and NFPA 10 is related to the selection and installation of portable fire extinguishers. None of these covers the specific area of standardized symbols relevant to the fire protection field like NFPA 170 does. Thus, NFPA 170 is uniquely positioned as the standard for symbols in fire protection.